linux-ext4 - Re: [PATCH] ext4: Fix return value for direct io reads at or beyond eof

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Message-ID: <5ACD0387.1050703@oracle.com>
Date:   Tue, 10 Apr 2018 11:33:43 -0700
From:   Ashish Samant <ashish.samant@...cle.com>
To:     linux-ext4@...r.kernel.org
Cc:     Ashish Samant <ashish.samant@...cle.com>, tytso@....edu
Subject: Re: [PATCH] ext4: Fix return value for direct io reads at or beyond
 eof

Hi,

Does this patch look ok? Gentle reminder for review.

Thanks,
Ashish

On 02/12/2018 01:18 PM, Ashish Samant wrote:
> Currently, an unaligned dio read at eof on ext4 returns EINVAL from
> do_blockdev_direct_IO. However this unaligned dio read at eof could be due
> to previous short read and we should return zero.
>
> Fix this by checking for this condition in ext4_direct_IO_read()
> and returning zero, if true.
>
> Signed-off-by: Ashish Samant <ashish.samant@...cle.com>
> ---
>   fs/ext4/inode.c | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 534a913..8b3dbc0 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -3806,7 +3806,7 @@ static ssize_t ext4_direct_IO_read(struct kiocb *iocb, struct iov_iter *iter)
>   	struct address_space *mapping = iocb->ki_filp->f_mapping;
>   	struct inode *inode = mapping->host;
>   	size_t count = iov_iter_count(iter);
> -	ssize_t ret;
> +	ssize_t ret = 0;
>   
>   	/*
>   	 * Shared inode_lock is enough for us - it protects against concurrent
> @@ -3814,6 +3814,8 @@ static ssize_t ext4_direct_IO_read(struct kiocb *iocb, struct iov_iter *iter)
>   	 * we are protected against page writeback as well.
>   	 */
>   	inode_lock_shared(inode);
> +	if (iocb->ki_pos >= i_size_read(inode))
> +		goto out_unlock;
>   	ret = filemap_write_and_wait_range(mapping, iocb->ki_pos,
>   					   iocb->ki_pos + count - 1);
>   	if (ret)